Plasma apparatus and production method thereof

ABSTRACT

A plasma apparatus includes a container ( 11 ) having an opening, a dielectric member ( 13 ) supported by an end surface of an outer periphery of the opening of the container ( 11 ), an electromagnetic field supplying means for supplying an electromagnetic field into the container ( 11 ) through the dielectric member ( 13 ), and a shield member ( 12 ) covering the outer periphery of the dielectric member ( 13 ) and shielding the electromagnetic field. A distance L 1  from an inner surface of the container ( 11 ) to an inner surface of the shield member ( 12 ) at an end surface of the container ( 11 ) is approximately N/2 (N is an integer not smaller than 0) times the wavelength of the electromagnetic field in an area ( 18 ) surrounded by the end surface of the container ( 11 ), the electromagnetic field supplying means and the shield member ( 12 ).

TECHNICAL FIELD

The present invention relates to a plasma apparatus generating plasma byan electromagnetic field supplied to a container and to a method ofmanufacturing the same.

BACKGROUND ART

Plasma apparatuses are widely used in manufacturing semiconductordevices and flat panel displays, to perform processes such as oxide filmformation, crystal growth of a semiconductor layer, etching and ashing.Among such plasma apparatuses, there is a high frequency plasmaapparatus that supplies a high frequency electromagnetic field to acontainer using an antenna, and generates high frequency plasma usingthe electromagnetic field. The high frequency plasma apparatus iscapable of generating plasma stably even when plasma gas pressure isrelatively low, and hence, application thereof is wide.

FIG. 8 shows an exemplary configuration of a conventional high frequencyplasma apparatus. This figure shows some parts in vertical crosssection. FIGS. 9A and 9B are cross sections showing, in enlargement, theportion IX surrounded by dotted lines in FIG. 8.

As shown in FIG. 8, the plasma apparatus has a cylindrical processingcontainer 511 with a bottom, opened at the upper portion. At the bottomof processing container 511, a mounting table 522 is fixed, and asubstrate 521 is placed on an upper surface of mounting table 522. On asidewall of processing container 511, a gas supply nozzle 517 isprovided, and at the bottom of processing container 511, an exhaust port516 is provided for vacuum evacuation. At the upper opening ofprocessing container 511, a dielectric plate 513 is arranged, and at ajoint portion between an upper surface of the sidewall of processingcontainer 511 and a peripheral portion of a lower surface of dielectricplate 513, an O-ring 514 as a sealing member is interposed, to attaintight sealing of the joint portion.

On dielectric plate 513, a radial antenna 530 is arranged. At thecentral portion of radial antenna 513, a high frequency generator 545generating a high frequency electromagnetic field is connected by awave-guide. At the upper surface of the sidewall of processing container511, an annular shield member 512 is arranged. Shield member 512 coversan outer periphery of dielectric plate 513 and radial antenna 530, so asto prevent leakage of the electromagnetic field to the outside ofprocessing container 511.

Of the electromagnetic field emitted from radial antenna 530, anelectromagnetic field F that has passed through dielectric plate 513 andintroduced to processing container 511 causes electrolytic dissociationof a gas in processing container 511, to generate plasma in an upperspace S2 above substrate 521. Here, an electromagnetic field F1 that isnot absorbed by the plasma and reflected and an electromagnetic field F2not directly introduced from radial antenna 530 to processing container511 are repeatedly reflected in an area S1 between an emitting surfaceof radial antenna 530 and a plasma surface, forming a standing wave. Thestanding wave also takes a part in the generation of plasma.

In the conventional plasma apparatus, when shield member 512 is arrangedat an upper surface of the sidewall of processing container 511, adistance L₁ from an edge 511A of an inner surface of the sidewall ofprocessing container 511 to an inner surface of shield member 512 is notat all considered. It is noted, however, that when wavelength of anelectromagnetic field in a recessed portion 518 (dotted area in FIGS. 9Aand 9B) formed by the upper surface of the sidewall of processingcontainer 511, the emitting surface of radial antenna 530 and the innersurface of shield member 512 is given as λg and the distance L₁ isapproximately λ_(g)/4 as shown in FIG. 9A, the voltage at the positionof edge 511A becomes large, possibly resulting in an abnormal discharge,as the position of edge 511A, that is the opening of recessed portion518, corresponds to the bulged portion of the standing wave. If such anabnormal discharge occurs, metal atoms of processing container 511 maybe dissociated, causing contamination in processing container 511.

In the conventional plasma apparatus, a distance L₂ from the innersurface of shield member 512 to the position where O-ring 514 isarranged is not at all considered, either. When the distance L₂ isapproximately λ_(g)/4, elasticity of O-ring 514 degrades because of thestrong electromagnetic field of the standing wave, and the life ofO-ring 514 becomes shorter.

DISCLOSURE OF THE INVENTION

The present invention was made to solve the above described problem, andits object is to suppress contamination in the container in which plasmais generated.

Another object is to elongate life of a sealing member such as theO-ring.

In order to attain these objects, the present invention provides aplasma apparatus, including: a container having an opening; a dielectricmember supported by an end surface of an outer periphery of the openingof the container and closing the opening; electromagnetic fieldsupplying means for supplying an electromagnetic field from the openinginto the container through the dielectric member; and a shield memberextending at least between the end surface of the container and theelectromagnetic field supplying means, covering an outer periphery ofthe dielectric member and shielding the electromagnetic field; whereinthe distance from an inner surface of the container at an end surface ofthe container to an inner surface of the shield member corresponds toapproximately N/2 (N is an integer not smaller than 1) times thewavelength of the electromagnetic field in an area surrounded by the endsurface of the container, the electromagnetic field supplying means andthe shield member. Accordingly, the position of the inner surface of thecontainer approximately corresponds to a node of the standing wavegenerated in the area mentioned above, and hence, the voltage at thisposition attains to approximately zero. Thus, abnormal discharge doesnot occur at this position. The distance is determined in considerationof relative dielectric constant of the dielectric member in the areamentioned above.

Here, desirably, when a distance between an end surface of the containerand the antenna is represented by D, relative air density in the area isrepresented by δ and wavelength of the electromagnetic field in the areais represented by λ_(g), the distance L₁ from the inner surface of thecontainer to the inner surface of the shield member satisfy the relationof(N/2)·λ_(g) −ΔL<L ₁<(N/2)·λ_(g) +ΔL

whereL ₁>0ΔL=(θ/360)·λ_(g)θ=sin⁻¹ (1/Γ)Γ=1+{0.328/(δ·D)^(1/2)}.

Further, a sealing member is interposed at a joint portion between theend surface of the container and the dielectric member for tight-sealingthe joint portion, and the sealing member is arranged at a position awayfrom the inner surface of the shield member by a distance approximatelyM/2 (M is an integer not smaller than 0 and not larger than N) times thewavelength of the electromagnetic field in the area mentioned above. Theposition where the sealing member is arranged approximately correspondsto the position of a node of the standing wave generated in the areamentioned above, and therefore, the electromagnetic field of thestanding wave is weak.

Desirably, when a distance between an end surface of the container andthe antenna is represented by D, relative air density in the area isrepresented by δ and wavelength of the electromagnetic field in the areais represented by λ_(g), the distance L₂ from the inner surface of theshield member to the position of arrangement of the sealing membersatisfy the relation of(M/2)·λ_(g) −ΔL<L ₂<(M/2)·λ_(g) +ΔL

whereL ₂>0ΔL=(θ/360)·λ_(g)θ=sin⁻¹(1/Γ)Γ=1+{0.328/(δ·D)^(1/2)}.

The plasma apparatus of the present invention includes a containerhaving a through hole formed therein, to which a conductor is inserted;an electromagnetic field supplying means for supplying anelectromagnetic field into the container; and a shield member closingthe through hole of the container to shield the electromagnetic field;wherein the distance from an inner surface of the container in thethrough hole of the container to an inner surface of the shield membercorresponds to approximately N/2 (N is an integer not smaller than 1)times the wavelength of the electromagnetic field in the through hole.Accordingly, the position of the inner surface of the containerapproximately corresponds to a node of the standing wave generated inthe through hole, and hence, the voltage at this position attains toapproximately zero. Thus, abnormal discharge does not occur at thisposition. An example of a conductor inserted into the through holeincludes a probe for measuring plasma density.

Desirably, when diameter of the through hole of the container isrepresented by D, relative air density in the through hole isrepresented by δ and wavelength of the electromagnetic field in thethrough hole is represented by λ_(g), the distance L₃ from the innersurface of the container to the inner surface of the shield membersatisfies the relation of(N/2)·λ_(g) −ΔL<L ₃<(N/2)·λ_(g) +ΔL

whereL ₃>0ΔL=(θ/360)·λ_(g)θ=sin⁻¹(1/Γ)Γ=1+{0.328/(δ·D)^(1/2)}.

Further, a sealing member tightly sealing the through hole of thecontainer is arranged at a position away from the inner surface of theshield member, at distance corresponding to approximately M/2 (M is aninteger not smaller than 0 and not larger than N) times the wavelengthof the electromagnetic field in the through hole. The position where thesealing member is arranged approximately corresponds to the position ofa node of the standing wave generated in the through hole, andtherefore, the electromagnetic field of the standing wave is weak.

Desirably, when diameter of the through hole of the container isrepresented by D, relative air density in the through hole isrepresented by δ and wavelength of the electromagnetic field in thethrough hole is represented by λ_(g), distance L₄ from the inner surfaceof the shield member to the position of arrangement of the sealingmember satisfies the relation of(M/2)·λ_(g) −ΔL<L ₄<(M/2)·λ_(g) +ΔL

whereL ₄>0ΔL=(θ/360)·λ_(g)θ=sin⁻¹(1/Γ)Γ=1+{0.328/(δ·D)^(1/2)}.

The present invention provides a method of manufacturing a plasmaapparatus, including: a container having an opening; a dielectric membersupported by an end surface of an outer periphery of the opening of thecontainer and closing the opening; electromagnetic field supplying meansfor supplying an electromagnetic field from the opening into thecontainer through the dielectric member; and a shield member extendingat least between the end surface of the container and the magnetic fieldsupplying means, covering an outer periphery of the dielectric memberand shielding the electromagnetic field; wherein distance from an innersurface of the container at an end surface of the container to an innersurface of the shield member is adjusted to approximately N/2 (N is aninteger not smaller than 1) times the wavelength of the electromagneticfield in an area surrounded by the end surface of the container, theelectromagnetic field supplying means and the shield member.

Further, a sealing member sealing a joint portion between the endsurface of the container and the dielectric member is arranged at aposition away from the inner surface of the shield member, at a distancecorresponding to approximately M/2 (M is an integer not smaller than 0and not larger than N) times the wavelength of the electromagnetic fieldin the area mentioned above.

Further, when the electromagnetic field supplying means is implementedby an antenna positioned opposite to the dielectric member, thewavelength of the electromagnetic field in an area surrounded by the endsurface of the container, the antenna and the shield member may beadjusted by changing an interval between the dielectric member and theantenna.

The present invention provides a method of manufacturing a plasmaapparatus including: a container having a through hole formed therein,to which a conductor is inserted; an electromagnetic field supplyingmeans for supplying an electromagnetic field into the container; and ashield member closing the through hole of the container to shield theelectromagnetic field; wherein distance from an inner surface of thecontainer in the through hole of the container to an inner surface ofthe shield member is adjusted to approximately N/2 (N is an integer notsmaller than 1) times the wavelength of the electromagnetic field in thethrough hole. An example of a conductor inserted into the through holeincludes a probe for measuring plasma density.

Further, a sealing member sealing the through hole of the container isarranged at a position away from the inner surface of the shield member,at a distance corresponding to approximately M/2 (M is an integer notsmaller than 0 and not larger than N) times the wavelength of theelectromagnetic field in the through hole,

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a configuration of an etching apparatus in accordancewith a first embodiment of the present invention.

FIG. 2 is a cross section showing, in enlargement, a portion IIsurrounded by dotted lines in FIG. 1.

FIG. 3 shows dependency of equivalent relative dielectric constant andshortening coefficient of wavelength on dielectric occupation ratio.

FIG. 4 represents a configuration of an etching apparatus in accordancewith a second embodiment of the present invention.

FIG. 5 is a cross section showing, in enlargement, a portion Vsurrounded by dotted lines in FIG. 4.

FIG. 6 represents a configuration of an ECR etching apparatus inaccordance with a third embodiment of the present invention.

FIG. 7 is a cross section showing, in enlargement, a portion VIIsurrounded by dotted lines in FIG. 6.

FIG. 8 represents an exemplary configuration of a conventional highfrequency plasma apparatus.

FIGS. 9A and 9B are cross sections showing, in enlargement, a portion IXsurrounded by dotted lines in FIG. 8.

BEST MODES FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described withreference to the drawings. Here, an example in which the plasmaapparatus in accordance with the present invention is applied to anetching apparatus will be described.

First Embodiment

FIG. 1 represents a configuration of an etching apparatus in accordancewith a first embodiment of the present invention. This figure shows someparts in vertical cross section.

The etching apparatus includes a cylindrical processing container 11with a bottom, opened at an upper portion. Processing container 11 isformed of a metal such as aluminum.

At a sidewall of processing container 11, a nozzle 17 is provided forintroducing a plasma gas such as Ar and an etching gas such as CF₄ intoprocessing container 11. Nozzle 17 is formed, for example, by a quartzpipe.

At the bottom of processing container 11, an insulating plate 15 formedof ceramic or the like is provided. Further, an exhaust port 16 isprovided penetrating through insulating plate 15 and the bottom ofprocessing container 11, and by means of a vacuum pump (not shown)communicated with exhaust port 16, the inside of processing containercan be evacuated to a desired degree of vacuum.

In processing container 11, a columnar mounting table 22 is contained,on an upper surface of which a substrate 21 as an object of processingis placed. Mounting table 22 is supported by an elevating shaft 23passing, with a play, through the bottom of processing container 11, tobe freely movable upward and downward. Further, to mounting table 22, abiasing high frequency power supply 26 is connected through a matchingbox 25. Output frequency of high frequency power supply 26 is aprescribed frequency within the range of several hundred kHz to ten andseveral MHz. In order to ensure air-tightness of processing container11, a bellows 24 is provided to surround elevation shaft 23, betweenmounting table 22 and insulating plate 15.

At the opening of processing container 11, a dielectric plate 13 formedof quartz glass or ceramic (for example, AL₂O₃, AlN) having thethickness of about 20 to about 30 mm is arranged. Dielectric plate 13 islarger in diameter than the opening, and dielectric plate 13 issupported by an upper surface of the sidewall, that is, an outerperiphery of the opening of processing container 11 (end surface ofprocessing container 11). At a joint portion between the upper surfaceof the sidewall of processing container 11 and a lower surface of aperiphery of dielectric plate 13, an O-ring 14 is interposed as asealing member, to tightly seal the joint portion. O-ring 14 is formed,for example, by Viton (vinylidene fluoride-hexafluoropropylene).

On dielectric plate 13, a radial antenna 30 is arranged, aselectromagnetic field supplying means for supplying an electromagneticfield to the inside of processing container 11 through dielectric plate13. Radial antenna 30 is separated from processing container 11 bydielectric plate 13, and protected from the plasma generated inprocessing container 11.

Further, on the upper surface of the sidewall of processing container11, an annular shield member 12 is arranged, covering outer peripheriesof dielectric plate 13 and radial antenna 30. Shield member 12 is formedof a metal such as aluminum, and has a function of shielding theelectromagnetic field. This shield member 12 prevents leakage of theelectromagnetic field to the outside of processing container 11. It isnoted that the shielding member may have such a structure that extendsat least between the upper surface of the sidewall of processingcontainer 11 and the lower surface of radial antenna 30 and covers theouter periphery of dielectric plate 13.

Radial antenna 30 includes two circular conductor plates 31, 32 parallelto each other and forming a radial wave-guide 33, and a conductor ring34 connecting peripheral portions of conductor plates 31 and 32. At thecentral portion of conductor plate 32 serving as an upper surface ofradial wave-guide 33, an inlet 35 is formed for introducing theelectromagnetic field into radial wave-guide 33, and in conductor plate31 serving as a lower surface of radial wave-guide 33, a plurality ofslots 36 are formed to supply the electromagnetic field propagatingthrough radial wave-guide 33 into processing container 11. Conductorplate 31 serves as the emitting surface of radial antenna 30.

When the wavelength of the electromagnetic field in radial wave-guide 33is represented as λ_(g1), an interval between the slots along the radialdirection of conductor plate 31 may be set approximately to λ_(g1), toprovide a radial type antenna, or the interval may be set approximatelyto λ_(g1)/20 to λ_(g1)/30 to provide a leak type antenna. Conductorplates 31, 32 and conductor ring 34 are formed of a metal such as copperor aluminum.

To the central portion of radial antenna 30, a coaxial line 41 isconnected. An outer conductor 41A of coaxial line 41 is connected toinlet 35 of conductor plate 32. An inner conductor 41B of coaxial line41 has its tip end formed to have a conical shape, and the bottomportion of the cone is connected to the center of conductor plate 31.

Coaxial line 41 connected to the central portion of radial antenna 30 inthis manner is connected to a high frequency generator 45 through arectangular coaxial transducer 42 and a rectangular wave-guide 43. Highfrequency generator 45 generates a high frequency electromagnetic fieldof a prescribed frequency (for example, 2.45 GHz) within the range of 1GHz to ten and several GHz. By providing a matching circuit 44 forimpedance matching in the middle of rectangular wave-guide 43,efficiency of power use can be improved. The path from high frequencygenerator 44 to radial antenna 30 may be connected by a cylindricalwave-guide.

FIG. 2 is a cross section showing, in enlargement, a portion IIsurrounded by dotted lines in FIG. 1.

Wave length of an electromagnetic field in a recessed portion (dottedarea in FIG. 2) formed by the upper surface of the sidewall ofprocessing container 11, the emitting surface (conductor plate 31) ofradial antenna 30 and the inner surface of shielding member 12 isrepresented as λ_(g), and shielding member 12 is arranged such that thedistance L₁ from an edge 11A of the inner surface of the sidewall ofprocessing container 11 to the inner surface of shielding member 12(that is, the depth from the opening of recessed portion 18 to the endsurface) is approximately λ_(g)/2. Further, O-ring 41 is arranged at adistance L₂, slightly shorter than λ_(g)/2, from the inner surface ofshielding member 12.

The wavelength λ_(g) of the electromagnetic field in recessed portion 18is represented in the following manner. First, the thickness andrelative dielectric constant of dielectric plate 13 are represented asd₁, ε₁, the distance and relative dielectric constant between dielectricplate 13 and emitting surface (conductor plate 31) of radial antenna 30are represented as d₂, ε₂, and d₁+d₂=d. Then, equivalent relativedielectric constant ε_(r) outside the radial antenna 30 is given byε_(r)=ε₁·ε₂/[ε₁·(1−α)+ε₂·α]  (1)where α is d₁/d, which is referred to as dielectric occupation ratio.When the wavelength of the electromagnetic field in a free space isrepresented as λ, the wavelength λ_(g) in recessed portion 18 is givenby the following equation, using the equivalent relative dielectricconstant ε_(r).λ_(g)=λ/(ε_(r))^(1/2)  (2)

where 1/(ε_(r))^(1/2) is referred to as shortening coefficient ofwavelength.

FIG. 3 shows dependency of equivalent relative dielectric constant andshortening coefficient of wavelength on dielectric occupation ratio. Theabscissa represents dielectric occupation ratio α, and the ordinaterepresents equivalent relative dielectric constant ε_(r) and shorteningcoefficient of wavelength 1/(ε_(r))^(1/2). Here, relative dielectricconstant ε₁ of dielectric plate 13 is assumed to be 4, and relativedielectric constant ε₂ of the space between dielectric plate 13 andradial antenna 30 is assumed to be 1.

As can be seen from this figure, when dielectric occupation ratio αchanges, the equivalent relative dielectric constant ε_(r) outsideradial antenna 30 changes, and shortening coefficient of wavelength1/(ε_(r))^(1/2) changes. Accordingly, the wavelength λ_(g) of theelectromagnetic field in recessed portion 18 also changes. Thedielectric occupation ratio α changes in accordance with the thicknessd₁ of dielectric plate 13 or the interval d₂ between dielectric plate 13and radial antenna 30. Therefore, by way of example, by changing theinterval d₂ between dielectric plate 13 and radial antenna 30 by movingradial antenna 30 upward/downward, it is possible to change thewavelength λ_(g) such that the distances L₁ and L₂ attain approximatelyto λ_(g)/2.

An operation of the etching apparatus shown in FIG. 1 will be described.

The inside of processing container 11 is evacuated to a degree of vacuumof about 0.01 to about 10 Pa, with substrate 21 placed on the uppersurface of mounting table 22. While maintaining the degree of vacuum, Aras the plasma gas and CF₄ as the etching gas are supplied. In thisstate, the electromagnetic field from high frequency generator 45 issupplied through rectangular wave-guide 43, rectangular coaxialtransducer 42 and coaxial line 41 to radial antenna 30.

The electromagnetic field introduced to radial antenna 30 propagatesradially from the central portion to the outer periphery of radialwave-guide 33 while being emitted little by little through a pluralityof slots 36. The electromagnetic field F emitted from radial antenna 30passes through dielectric plate 13 and introduced into processingcontainer 11 to cause electrolytic dissociation of Ar in processingcontainer 11, generate plasma in the space S2 above substrate 21 and todissociate CF₄.

The plasma has its energy and anisotropy controlled by a bias voltageapplied to mounting table 22, and it is utilized together with radicalCF_(x)(x=1, 2, 3) adhered to substrate 21 for the etching process.

Similar to the conventional example, the electromagnetic field F1 notabsorbed by the generated plasma but reflected and the electromagneticfield F2 not directly introduced from radial antenna 30 to processingcontainer 11 are repeatedly reflected between the emitting surface(conductor plate 31) of radial antenna 30 and the plasma surface,forming a standing wave.

In the etching apparatus, as shown in FIG. 2, the distance L₁ from theedge 11A of processing container 11 to the inner surface of shieldmember 12 is approximately λ_(g)/2. Therefore, the position of edge 11Aapproximately corresponds to a node of the standing wave. Therefore, thevoltage between edge 11A and the emitting surface (conductor plate 13)at the opposing position attains approximately zero, and hence, abnormaldischarge does not occur at edge 11A. Thus, contamination of processingcontainer 11 caused by the abnormal discharge can be prevented.

Further, the distance L₂ from the inner surface of shield member 12 toO-ring 14 is also approximately λ_(g)/2. Therefore, the position ofO-ring 14 also approximately corresponds to a node of the standing wave,where the electromagnetic field of the standing wave is weak.Accordingly, the influence of the standing wave to O-ring 14 becomessmaller. Thus, the life of O-ring 14 can be made longer.

In the foregoing, an example has been described in which the distance L₁from edge 11A of processing container 11 to the inner surface of shieldmember 12 is approximately λ_(g)/2. What is necessary is simply that theedge 11A is approximately positioned at the node of the standing wave,and therefore, the distance L₁ may be about N/2 times λ_(g) (N is aninteger not smaller than 1).

Similarly, the distance L₂ from the inner surface of shield member 12 toO-ring 14 should approximately be M/2 times λ_(g) (M is an integer notsmaller than 0 and not larger than N). It is noted, however, that whenN≠M, it follows that the bulge of the standing wave exists on the innerside of processing container 11 when viewed from O-ring 14. If anabnormal discharge should occur, metal atoms dissociated from processingcontainer 11 by electron impact would dissipate in processing container11 and contaminate processing container 11. Therefore, it is desirableto set the values N=M, so that O-ring 14 is positioned slightly closerto the side of shield member 12 when viewed from edge 11A.

It is not necessary that distances L₁ and L₂ are exactly λ_(g)·N/2 andλ_(g)·M/2. Tolerable ranges of L₁ and L₂ will be described.

In a uniform electric field generated by parallel plate electrodes, therelation between electric field intensity E₁ and an equivalent distanceD [cm] between electrodes when spark discharge is generated in an ACelectric field is given by the following equation:E ₁=24.05δ[1+[0.328/(δ·D)^(1/2)]][kV/cm]  (3)

Here, δ is referred to as relative air density, which represents airdensity with the air density at a normal temperature and atmosphericpressure (20° C., 1013 hPa) being 1, given byδ=0.289p/(273+t)  (4)

Here, p represents pressure [hPa] and t represents temperature [° C.].

When the relation represented by the equation (3) is applied to theconfiguration shown in FIG. 2, the parallel plate electrodes that formthe uniform electric field correspond to the upper surface of thesidewall of processing container 11 and the emitting surface (conductor31) of radial antenna 30. Therefore, equivalent distance D betweenelectrodes in equation (3) corresponds to the diameter of recessedportion 18. Here, the vacuum portion between the upper surface of thesidewall and dielectric plate 13 is neglected, and hence, equivalentdistance D between electrodes is given byD=(ε₁)^(1/2) ·d ₁+(ε₂)^(1/2) ·d ₂  (5)

With the value D being set to infinite in equation (3), the electricfield intensity E₂ when a spark discharge occurs in a non-uniformelectric field is given, as represented by the following equation.E ₂=24.05δ[kV/cm]  (6)

This represents the condition when a spark discharge occurs at the edge11A of the inner surface of the sidewall of processing container 11.

The ratio between equations (3) and (6) will beΓ=E ₁ /E ₂=1+[0.328/(δ·D)^(1/2)]  (7)

When the voltage at edge 11A is not higher than (1/Γ) of the peakvoltage, it is considered that discharge at edge 11A would not occur.The angle θ at which the voltage attains to 1/Γ of the peak voltage isgiven byθ=sin⁻¹(1/Γ)[° ]  (8)and therefore, the tolerable value ΔL of L₁ and L₂ isΔL=(θ/360)·λ_(g)  (9)Accordingly, the values L₁ and L₂ may be set to be in the followingranges.(N/2)·λ_(g) −ΔL<L ₁<(N/2)·λ_(g) +ΔL  (10)(M/2)·λ_(g) −ΔL<L ₂<(M/2)·λ_(g) +ΔL  (11)

A specific example will be described. In the configuration shown in FIG.2, when there are quartz glass (dielectric plate 13) having thethickness of d₁=3.1 [cm] and relative dielectric constant ε₁=3.8 and air(space between dielectric plate 13 and radial antenna 30) having thethickness of d₂=0.5 [cm] and relative dielectric constant ε₁=1.0 betweenthe electrodes, equivalent distance D between electrodes is 6.5 [cm]according to equation (5). When pressure p=1013 [hPa] and temperaturet=40 [° C.] in equation (4), θ=61.9 [° ] from equations (7) and (8).Here, equivalent relative dielectric constant ε_(r) between theelectrodes is 2.73 according to equation (1), and therefore, accordingto equation (2), the wavelength λ_(g) of the electromagnetic fieldhaving the frequency of 2.45 [GHz] is 7.4 [cm]. Therefore, the tolerableranges of L₁ and L₂ are as follows, by inputting values θ and λ_(g) intoequations (9) to (11).(3.7·N−1.27)[cm]<L ₁<(3.7·N+1.27)[cm](3.7·M−1.27)[cm]<L ₂<(3.7·M+1.27)[cm]

where L₁ and L₂ are both positive values.

The condition above is a limitation determined to prevent discharge, andit is not the case that dissociation of metal atoms from processingcontainer 11 by impact of electrons in the plasma is prevented.

Second Embodiment

FIG. 4 represents a configuration of an etching apparatus in accordancewith a second embodiment of the present invention. In the figure,portions similar to those of FIG. 1 will be denoted by the samereference characters and description thereof will appropriately beomitted. FIG. 5 is a cross section showing, in enlargement, a portion Vsurrounded by dotted lines in FIG. 4.

The etching apparatus shown in FIG. 4 has a circular through hole 19formed in a sidewall of processing container 11, through which aconductor probe 51 for measuring plasma density is inserted. Probe 51 isarranged at the central axis of through hole 19, and together with theinner surface of through hole 19, forms a coaxial line. A coaxial linedoes not have high-frequency cut-off, and therefore, it is often usedfor plasma density measurement in a high frequency plasma apparatus.Probe 51 has one end connected to the body of plasma density measuringapparatus arranged outside of processing container 11, and the other endextending to the inside of processing container 11.

Through hole 19 formed in the sidewall of processing container 11 istightly sealed by an O-ring 53 as a sealing member interposed on probe51, so that air-tightness of processing container 11 is ensured.

Further, that side of through hole 19 which is on the side of the outersurface of the sidewall is closed by means of a shield member 54, and anelectric field going to the outside of processing container 11 throughthis hole is shielded. Probe 51 is taken out of processing container 11through the central portion of shield member 54, and an insulatingmember 55 such as shown in FIG. 5 is interposed to prevent contactbetween probe 51 and shield member 54.

When wavelength of an electric field in a recessed portion 56 formed bythe inner surface of through hole 19 and the inner surface of shieldmember 54 is represented as λ_(g), shield member 54 is arranged suchthat the distance L₃ from an edge 11B of the inner surface of thesidewall of processing container 11 to the inner surface of shieldmember 54 (that is, the depth from an opening of recessed portion 56 tothe end surface) is approximately N/2 times λ_(g). Further, O-ring 14 isarranged such that the distance L₄ from the inner surface of shieldmember 12 is approximately M/2 times λ_(g). The tolerable range of L₃ isrepresented by equation (10) above with the value L₁ replaced by L₃, andthe range of L₄ is represented by equation (11) above with the value L₂replaced by L₄.

Because of the foregoing, even when a standing wave appears in therecessed portion 56, abnormal discharge does not occur at edge 11B, andtherefore, contamination of processing container 11 can be suppressed.Further, as the electric field of the standing wave is weak at theposition of O-ring 54, the life of O-ring 54 can be made longer.

Third Embodiment

The present invention is also applicable to an ECR etching apparatusthat etches substrates using electron cyclotron resonance (ECR). FIG. 6represents a configuration of an ECR etching apparatus in accordancewith a third embodiment of the present invention. In the figure,portions similar to those of FIG. 1 will be denoted by the samereference characters and description thereof will appropriately beomitted.

As shown in FIG. 6, the etching apparatus has a vacuum container 111that includes a plasma chamber 111P having an electromagnetic coilforming a mirror magnetic field provided therearound, and a reactionchamber 111Q containing a substrate 21 as an object of processing. At anupper portion of plasma chamber 111P, a gas supply nozzle 117A supplyinga plasma gas such as Ar is provided, and at an upper portion of reactionchamber 111Q, an annular gas supply portion 117B supplying an etchinggas such as CF₄ is provided.

At an opening at the upper portion of plasma chamber 111P, a dielectricplate 113 is arranged. Dielectric plate 113 is supported by an uppersurface of the sidewall (end surface of vacuum container 111) thatcorresponds to the opening of plasma chamber 111P, and at the jointportion between the upper surface of the sidewall and a lower surface ofthe periphery of dielectric plate 113, an O-ring 114 is interposed as asealing member.

On dielectric plate 113, a wave-guide 144 is arranged, connected to ahigh frequency generator 145 generating a high frequency electromagneticfiled. In the ECR etching apparatus, wave-guide 144 and high frequencygenerator 145 constitute electromagnetic field supplying means. Further,on the upper surface of the sidewall of vacuum container 111, an annularshield member 112 is arranged, surrounding the outer periphery ofdielectric plate 113.

FIG. 7 is a cross section showing, in enlargement, a portion VIIsurrounded by dotted lines in FIG. 6.

When the wavelength of the electromagnetic field in a recessed portion118 (dotted area in FIG. 7) formed by the upper surface of the sidewallof vacuum container 111, the lower surface of wave-guide 144 and theinner surface of shield member 112 is represented as λ_(g), shieldmember 112 is arranged such that the distance L₅ from an edge 111A of aninner surface of the sidewall of vacuum container 111 to the innersurface of shield member 112 (that is, depth from an opening of recessedportion 118 to an end surface) is approximately λ_(g)/2. Further, O-ring114 is arranged at a distance L₆, slightly shorter than λ_(g)/2, fromthe inner surface of shield member 112. The tolerable range of L₅ isrepresented by equation (10) above with the value L₁ replaced by L₅, andthe range of L₆ is represented by equation (11) above with the value L₂replaced by L₆.

Because of the foregoing, even when a standing wave appears in therecessed portion 118, abnormal discharge does not occur at edge 111A,and therefore, contamination of vacuum container 111 can be suppressed.Further, as the electric field of the standing wave is weak at theposition of O-ring 114, the life of O-ring 114 can be made longer.

When a through hole through which a probe for measuring plasma densityis inserted is provided in the sidewall of vacuum container 111, thepositions where the shield member and the O-ring are arranged may beadjusted in the similar manner as described with reference to the secondembodiment.

Though examples in which the plasma apparatus in accordance with thepresent invention is applied to an etching apparatus have been describedin the foregoing, it is needless to say that the invention may beapplied to other plasma apparatus, such as a plasma CVD apparatus.

As described above, in the present invention, in an area surrounded bythe end surface of the container, the electromagnetic field supplyingmeans and the shield member, the distance from the inner surface of thecontainer to the inner surface of the shield member is adjusted to beapproximately N/2 (N is an integer not smaller than 1) times thewavelength of the electromagnetic field in the area. Consequently, theposition of the inner surface of the container comes to approximatelycorrespond to a node of the standing wave generated in the area, and thevoltage at this position attains approximately zero. Accordingly,abnormal discharge at the position of the inner surface of the containeris prevented, and contamination of the container can be prevented.

Further, in the present invention, a sealing member is arranged at aposition away from the inner surface of the shield member, by a distanceof approximately M/2 (M is an integer not smaller than 0 and not largerthan N) times the wavelength of the electromagnetic field in the area.This position approximately corresponds to a node of the standing wavegenerated in the area, and the electromagnetic field of the standingwave is weak. Therefore, the life of the sealing member can be madelonger.

When the electromagnetic field supplying means is implemented by anantenna positioned opposite to the dielectric member, the wavelength ofthe electromagnetic field in the area surrounded by the end surface ofthe container, the antenna and the shield member is adjusted by changingthe interval between the dielectric member and the antenna. Even whenthe distance between the inner surface of the container and the innersurface of the shield member is physically constant, the aforementioneddistance can be set approximately to N/2 times the wavelength of theelectromagnetic field, as the wavelength of the electromagnetic field inthe area is adjusted by changing the interval between the dielectricmember and the antenna.

From the same reason, even when the position where the sealing member isarranged is physically fixed, the distance from the inner surface of theshield member to the position of arrangement of the sealing member canbe set approximately to M/2 times the wavelength of the electromagneticfield, by changing the interval between the dielectric member and theantenna.

Further, in the present invention, in the through hole of the container,the distance from the inner surface of the container to the innersurface of the shield member is adjusted to be approximately N/2 (N isan integer not smaller than 1) times the wavelength of theelectromagnetic field in the through hole. Therefore, the position of aninner surface of the container comes to approximately correspond to anode of a standing wave generated in the through hole, and the voltageat this position approximately attains to zero. Thus, abnormal dischargedoes not occur at a position of the inner surface of the container, andcontamination of the container can be prevented.

Further, in the present invention, the sealing member is arranged at aposition away from the inner surface of the shield member, by a distanceof approximately M/2 (M is an integer not smaller than 0 and not largerthan N) times the wavelength of the electromagnetic field in the throughhole. This position approximately corresponds to a node of a standingwave formed in the through hole, and the electromagnetic field of thestanding wave is weak. Therefore, the life of the sealing member can bemade longer.

INDUSTRIAL APPLICABILITY

The present invention may be applied to a plasma apparatus for processessuch as oxide film formation, crystal growth of a semiconductor layer,etching and ashing, in manufacturing semiconductor devices or flat paneldisplays.

1. A plasma apparatus, comprising: a container (11) having an opening; adielectric member (13) supported by an end surface of an outer peripheryof the opening of said container and closing said opening; an antennafor supplying an electromagnetic field from said opening into saidcontainer through the dielectric member; and a shield member (12)extending at least between the end surface of said container and saidantenna, covering an outer periphery of said dielectric member andshielding said electromagnetic field; wherein a distance from an innersurface of said container at the end surface of said container to aninner surface of said shield member corresponds to approximately N/2 (Nis an integer not smaller than 0) times the wavelength of saidelectromagnetic field in an area surrounded by the end surface of saidcontainer, said antenna and said shield member, such that a distance L1from the inner surface of said container to the inner surface of saidshield member satisfies the relation:(N/2)·λ_(g) −ΔL<L ₁<(N/2)·λ_(g) +ΔL, whereL ₁>0,ΔL=(θ/360)·λ_(g),θ=sin⁻¹(1/Γ), andΓ=1+{0.328/(δ·D ^(1/2)}, wherein D is a distance between the end surfaceof said container (11) and said antenna, δ is the relative air densityin said area, and λ_(g) is a wavelength of said electromagnetic field insaid area.
 2. The plasma apparatus according to claim 1, furthercomprising: a sealing member (14) interposed at a joint portion betweenthe end surface of said container (11) and said dielectric member (13)for tight-sealing the joint portion; wherein the sealing member isarranged at a position away from the inner surface of said shield memberby a distance approximately M/2 (M is an integer not smaller than 0 andnot larger than N) times the wavelength of said electromagnetic field.3. The plasma apparatus according to claim 2, wherein when a distancebetween the end surface of said container and said antenna isrepresented by D, relative air density in said area is represented by δand wavelength of said electromagnetic field in said area is representedby λ_(g), a distance L₂ from the inner surface of said shield member tothe position of said sealing member satisfy the relation of(M/2)·λ_(g) −ΔL<L ₂<⁽ M/2)·λ_(g) +ΔL whereL ₂>0,ΔL=(θ/360)·λ_(g),θ=sin⁻¹(1/Γ)Γ=1+{0.328/(δ·D ^(1/2)}.